Introduction
The 3500/33 with assembly number 149986-01D is a Velocity Monitor Module for the Bently Nevada 3500 Machinery Protection System.
This module is designed to continuously monitor the casing vibration (absolute vibration) of critical machinery. It accepts input from seismic transducers, such as velocity sensors or accelerometers, and provides continuous protection by comparing the vibration velocity levels against user-configured alarm setpoints. If a dangerous condition is detected, it triggers alarms to alert operators or initiate a machine shutdown (trip), thereby preventing severe damage. It is the primary module for monitoring overall machine health from a structural perspective.
Key Parameters
The following table outlines the key specifications for the 3500/33 Velocity Monitor Module.
| Parameter Category | Specification |
|---|---|
| Part Number | 3500/33 (Module) / 149986-01D (Assembly) |
| Function | Dual-Channel Casing Vibration (Velocity) Monitor |
| Compatibility | Bently Nevada 3500 Series Racks |
| Input Channels | 2 independent channels |
| Input Signal | Accepts from velocity transducers or accelerometers (with IEPE conditioning) |
| Measured Parameter | Casing Vibration Velocity (in mm/s or in/s RMS or Peak) |
| Dynamic Signal Range | Adjustable for various transducer sensitivities |
| Alarm Relays | Per channel: Danger (Trip), Alert (Warning), OK (Buffered) |
| Power Supply | Powered from the 3500 rack backplane |
| Operating Temperature | -30 °C to +65 °C (-22 °F to +149 °F) |
| Primary Housing Material | Glass-Filled Thermoplastic (UL 94 V-0 rated) |
| Heat Sink Material | Aluminum |
| Connector Material | Plated Copper Alloy |
| PCB Material | FR-4 Glass Epoxy |
| Dimensions (H x W x D) | Approx. 193 mm x 57 mm x 200 mm (7.6 in x 2.25 in x 7.87 in) Standard 3500 module frame size |
| Weight | Approx. 0.8 kg (1.76 lbs) |
| Mounting | Slides into a slot in a 3500 series rack |
Application Scenarios
The 3500/33 module is a fundamental protection device used to monitor the overall mechanical health of a wide array of industrial machinery where the structure or casing vibration is a key indicator of problems.
Casing Vibration Monitoring on Rotating Equipment:
Pumps, Fans, Motors, and Blowers: Permanently installed to monitor the overall vibration levels of the machine's casing or bearing housings. It protects against mechanical faults like imbalance, misalignment, bearing wear, and structural resonance that are clearly transmitted to the machine casing.
Turbine and Compressor Bearing Housing Monitoring:
Steam Turbines, Gas Turbines, and Compressors: Used to monitor the absolute vibration of the bearing housings. This provides a crucial layer of protection alongside shaft vibration monitoring (from proximity probes), especially for machines with fluid film bearings where casing vibration is a direct indicator of dynamic forces.
General Machinery Protection in Various Industries:
Power Generation, Oil & Gas, Petrochemicals: Applied to any critical rotating asset where an overall vibration measurement is sufficient for protection and trending purposes. It is ideal for machines where installing shaft-relative proximity probes is not feasible or necessary.
Predictive Maintenance and Condition Monitoring:
The module provides 4-20 mA outputs proportional to vibration levels, which can be fed into a DCS or PLC for continuous trending. This allows maintenance teams to track the degradation of machine health over time and schedule repairs before a failure occurs, supporting a proactive maintenance strategy.
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